Raw material feeding apparatus for rotary hearth furnace

ABSTRACT

The invention provides a raw materials feeding apparatus capable of uniformly dispersing and feeding into a furnace agglomerated raw materials that are likely to undergo dusting, deformation and mutual adhesion. In a raw material feeding apparatus for a rotary hearth furnace, for feeding raw materials to a rotary hearth furnace by using a flat belt conveyor, the invention employs a construction in which a scraper for guiding the raw materials on the flat belt conveyor to a side surface of the flat belt conveyor is arranged obliquely to a traveling direction of the flat belt conveyor. Preferably, the scraper is arranged in such a manner as to guide the raw materials to both sides of the flat belt conveyor.

TECHNICAL FIELD

This invention relates to a pellet-feeding apparatus for a rotary hearthfurnace, for feeding raw material to a rotary hearth furnace by using aflat belt conveyor.

More concretely, the invention relates to a raw material-feedingapparatus feeding raw materials to a rotary hearth furnace for mainlyproducing reduced iron by using an iron ore or the wastes of ironmaking.

BACKGROUND ART

A rotary hearth furnace is a movable hearth furnace for heating andreducing metal oxides such as iron ore or the wastes of iron making, anda rotary hearth furnace, the hearth of which is a horizontal surface androtates, is known from Japanese Examined Patent Publication (Kokoku) No.45-19569, and so forth.

The raw-material processed inside this rotary hearth furnace is, inadvance, agglomerated and is charged into the rotary hearth by acharging device provided at an upper part of the furnace. Because anouter peripheral portion of the rotary hearth has a greater area thanits inner peripheral portion, however, contrivances are required so asto uniformly disperse the raw materials on the entire surface of therotary hearth. Therefore, a vibration conveyor and a swivel conveyorhave been used in the past for this uniform dispersion charging device.

Japanese Unexamined Patent Publication (Kokai) No. 11-293317, forexample, discloses a mechanism for charging a pellet (hereinafter called“raw material”) into a rotary hearth furnace, having the construction inwhich a plurality of screens for dividedly guiding the pellets isarranged in a trough of a vibration conveyor for charging the pellet tothe rotary hearth furnace and uniformly charges the pellets into therotary hearth furnace by adjusting openings of passages partitioned bythese screens.

Japanese Unexamined Patent Publication (Kokai) No. 11-337265 discloses amechanism for uniformly charging the pellets into the rotary hearthfurnace by adjusting a swivel speed in accordance with a position of apivot of the swivel conveyor.

However, the agglomerated raw material has various properties such aslow strength, brittleness, easy adhesion, etc, depending of thecondition of the raw material, formation method and water content.Therefore, the conventional method or the method using the vibrationconveyor, for example, is not able to satisfy the charging functionitself because it invites dusting, deformation and mutual adhesion, bythe application of vibration to the agglomerated raw material.

The swivel conveyor has theoretically only a function of charging theraw material onto the swivel orbit and is a system that cannot uniformlydisperse and charge the pellet.

DISCLOSURE OF THE INVENTION

To solve the problems of the prior art technologies described above, theinvention provides a raw material-feeding apparatus capable of uniformlydispersing, and feeding into a furnace, an agglomerated raw materialthat is likely to undergo dusting, deformation and mutual adhesion.Concretely, the invention is directed to the following points.

-   1) To employ a mechanism that minimizes the impact applied to a    agglomerated raw material.-   2) To feed the agglomerated raw material on a continuous line.-   3) To feed the agglomerated raw material into a rotary hearth    furnace without interruption.

The invention was completed as a result of intensive studies for solvingthe problems described above and provides a raw-material-feedingapparatus for a rotary hearth furnace, for feeding a raw material to arotary hearth furnace capable of uniformly dispersing and feeding aagglomerated raw material that is likely to undergo dusting, deformationand mutual adhesion, into a furnace by obliquely disposing a scraper forguiding the raw-material on the flat belt conveyor to a side surface ofthe flat belt conveyor with respect to a traveling direction of the flatbelt conveyor. The gist of the invention is described in the Scope ofClaim for Patent.

-   (1) A raw material-feeding apparatus for a rotary hearth furnace,    for feeding a raw material to a rotary hearth furnace by using a    flat belt conveyor, characterized in that a scraper for guiding the    raw material on the flat belt conveyor to a side surface of the flat    belt conveyor is arranged obliquely to a traveling direction of the    flat belt conveyor.-   (2) A raw material-feeding apparatus for a rotary hearth furnace    described in (1), wherein the scrapers for guiding the raw material    on the flat belt conveyor to the side surface of the flat belt    conveyor are disposed on both sides of the flat belt conveyor.-   (3) A raw material-feeding apparatus for a rotary hearth furnace    described in (1) or (2), wherein a gap between entrance portions of    the scraper for guiding the raw material on the flat belt conveyor    to the side surface of the flat belt conveyor is adjustable.-   (4) A raw material-feeding apparatus for a rotary hearth furnace    described in (1) or (2), wherein the scraper for guiding the raw    materials on the flat belt conveyor to the side surface of the flat    belt conveyor is shaped into a curve shape.-   (5) A raw material-feeding apparatus for a rotary hearth furnace    described in any of (1) to (4), wherein the raw material is charged    in one layer onto the flat belt conveyor.-   (6) A raw material-feeding apparatus for a rotary hearth furnace    described in any of (1) to (4), wherein the raw material is charged    in two to five layers onto the flat belt conveyor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a raw material-feeding apparatus for a rotary hearthfurnace according to an embodiment of the invention.

FIG. 2( a) is a plan view showing a raw material-feeding apparatus for arotary hearth furnace according to the embodiment of the invention inwhich a scraper is so arranged as to guide the raw material to one ofthe sides of a flat belt conveyor.

FIG. 2( b) is a perspective view showing a raw material-feedingapparatus for a rotary hearth furnace according to the embodiment of theinvention in which the scraper is so arranged as to guide the rawmaterial to one of the sides of a flat belt conveyor.

FIG. 3( a) is a plan view showing a raw material-feeding apparatus for arotary hearth furnace according to the embodiment of the invention inwhich the scraper is so arranged as to guide the raw material to bothsides of the flat belt conveyor.

FIG. 3( b) is a perspective view showing a raw material-feedingapparatus for a rotary hearth furnace according to the embodiment of theinvention in which the scraper is so arranged as to guide the rawmaterial to both sides of the flat belt conveyor.

FIG. 4( a) is a plan view showing an embodiment of the invention whereina drop chute of the raw material feeding apparatus for a rotary hearthfurnace according to the invention operates also as a cutoff plate forpreventing the fall of raw materials.

FIG. 4( b) is a perspective view showing an embodiment of the inventionwherein the drop chute of the raw material-feeding apparatus for arotary hearth furnace according to the invention operates also as thecutoff plate for preventing the fall of raw materials.

FIG. 5( a) is a plan view showing a raw material-feeding apparatus for arotary hearth furnace according to the invention wherein a scraper has acurve surface.

FIG. 5( b) is a perspective view showing the raw material-feedingapparatus for a rotary hearth furnace according to the invention whereinthe scraper has a curve surface.

FIG. 6 shows adjustment projections used in an embodiment of theinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the invention will be explained in detail with referenceto FIGS. 1 to 6.

FIG. 1 shows a raw material-feeding apparatus for a rotary hearthfurnace according to an embodiment of the invention.

Referring to FIG. 1, reference numeral 1 denotes a flat belt conveyor.Reference numeral 2 denotes a raw material. Reference numeral 3 denotesa scraper. Reference numeral 4 denotes an entrance gap adjustmentmechanism. Reference numeral 5 denotes a rotary hearth. Referencenumeral 7 denotes a falling raw material cutoff plate. Reference numeral8 denotes heat insulating structure.

The pellet 2 fed to the flat belt conveyor 1 is guided by the scraper 3to a side surface of the flat belt conveyor 1 and falls onto the rotaryhearth 5.

Though a small gap is shown secured between the scraper 3 and the flatbelt conveyor 1, this gap need not always be secured.

The invention can convey the raw material without imparting impactthereto because the invention employs the flat belt conveyor 1.

The materials of the conveyor belt of the flat belt conveyor 1 are of apolymer type such as rubber, or a metal, and preferably have high heatresistance.

In the embodiment shown in FIG. 1, the lower surface of a carrier of theflat belt conveyor 1 is supported by rollers aligned densely but may besupported by flat plates in place of the rollers.

Crown pulleys or an apparatus having a zigzag movement preventionfunction such as rollers having the V guides shown in FIG. 1 arepreferably provided to the flat belt conveyor 1.

To avoid radiation heat from inside the furnace to the flat beltconveyor 1, the heat insulating structure 8 or a water cooling structureis preferably provided to the bottom of the flat belt conveyor 1.

FIGS. 2( a) and 2(b) show a raw material feeding apparatus for a rotaryhearth furnace according to the invention, wherein the scraper of theinvention is disposed on one of the sides of the flat belt conveyor.FIG. 2( a) is a plan view and FIG. 2( b) is a perspective view.

Referring to FIGS. 2( a) and 2(b), reference numeral 1 denotes the flatbelt conveyor. Reference numeral 2 denotes the raw materials. Referencenumeral 3 denotes the scraper. Reference numeral 5 denotes the rotaryhearth. Reference numeral 6 denotes a fan. Reference numeral 7 denotesthe falling raw materials prevention cutoff plate. Reference numeral 8denotes the heat insulating structure. Reference numeral 9 denotes acleaner.

The raw materials 2 fed to the flat belt conveyor 1 slides in the sidesurface direction of the flat belt conveyor 1 while being guided by thescraper 3 arranged obliquely relative to the traveling direction of theflat belt conveyor 1 and falls onto the rotary hearth 5.

The raw materials slide gently and transversely to the side surfacedirection of the flat belt conveyor 1 along the scraper 3.

The raw materials reaching the side surface of the flat belt conveyorfalls serially and continuously from the belt and a continuous anduniform feed becomes possible on a continuous line.

To prevent sticking of the raw materials 2, adjustment projections 10for correcting and adjusting uniform dispersion of the raw materials arepreferably disposed on the surface of the scraper 3 on which the rawmaterial flows, as shown in FIG. 6. The adjustment projections 10 can beapplied to the embodiments shown in FIGS. 3( a) and 3(b) and FIGS. 4( a)and 4(b), too.

Though a plurality of scrapers 3 is disposed in the embodiment, thescraper 3 may be a single scraper.

When the raw material is likely to undergo deformation or to adhere, itis preferred to reduce mutual bonding power at the time of transversesliding by disposing a plurality of scrapers 3. A single scraper nothaving the feed line is preferable when large variance exists in thesize of the raw material.

To prevent deformation and adhesion of the raw material, polymer typerubber, resins such as Teflon (trade mark) and metal materials havinghigh wear resistance (stainless steel, etc) are individually used as thematerial of the scraper 3, or can be bonded to the scraper 3 to form amulti-layered material.

The falling raw material prevention cutoff plate 7 is disposed toprevent the falling raw material from the carrier surface of the flatbelt conveyor 1 down to the inside. However, a drop chute may operate asthe cutoff plate 7 for preventing the falling raw material.

To prevent overheat of the flat belt conveyor 1, cooling air ispreferably blown by the fan 6, etc, into the space sandwiched betweenthe carrier surface of the flat belt conveyor 1 and a return surface.

The cleaner 9 for scraping off and removing adhering matters to the beltis preferably disposed downstream of the flat belt conveyor 1.

The belt speed of the flat belt conveyor 1 is preferably variable inorder to control the feed amount of the raw material, to adjust thethickness of the raw material layer on the belt and to uniformlydisperse the pellet.

When the raw material is dividedly charged by using a plurality ofscrapers 3, the gaps of the entrance portion of the scrapers 3 ispreferably adjustable. When the entrance gaps are adjustable, the feedamount of each line becomes adjustable.

The gap of the entrance portion of the scraper 3 is preferably adjustedby fixing the scraper 3 by an elongated hole and changing theinstallation position of the scraper 3 as the entrance gap adjustmentmechanism 4 shown in FIG. 1. This entrance gap adjustment mechanism 4can be applied to the embodiments shown in FIGS. 3( a) and 3(b) andFIGS. 4( a) and 4(b).

When the gap of the entrance portion of the scraper for feeding the rawmaterials to the outer peripheral portion of the rotary hearth is madegrater than that of the entrance portion of the scraper for feeding theraw materials to the inner peripheral portion by utilizing thismechanism 4, a greater amount of the raw materials can be fed to theouter peripheral portion having a greater area and a difference in thefeed amount resulting from the area difference between the inner andouter circumferences of the rotary hearth can be corrected.

FIGS. 3( a) and 3(b) show a raw material-feeding apparatus for a rotaryhearth according to another embodiment of the invention, wherein thescrapers of the invention are disposed on both sides of the flat beltconveyor. FIG. 3( a) is a plan view and FIG. 3( b) is a perspectiveview.

Referring to FIGS. 3( a) and 3(b), reference numeral 1 denotes the flatbelt conveyor. Reference numeral 2 denotes the raw materials. Referencenumeral 3 denotes the scraper. Reference numeral 5 denotes the rotaryhearth. Reference numeral 6 denotes the fan. Reference numeral 7 denotesthe falling raw material prevention cutoff plate. Reference numeral 8denotes the heat insulating structure.

As the scrapers 3 are disposed on both sides of the flat belt conveyor 1in this embodiment, the raw materials are allowed to fall from both sidesurfaces of the flat belt conveyor 1 and can be fed to the rotary hearth5.

In this case, the uniform dispersion charging effect of the raw materialcan be improved by alternately arranging the entrance positions of theright and left scrapers.

FIGS. 4( a) and 4(b) shows another embodiment, wherein the drop chute ofthe raw material-feeding apparatus for a rotary hearth in the inventionis allowed to operate as the cutoff plate for preventing the falling rawmaterial. FIG. 4( a) is a plan view and FIG. 4( b) is a perspectiveview.

The falling raw material prevention cutoff plate 7 shown in FIGS. 4( a)and (b) is inclined and has the function of a drop chute of the rawmaterial, too.

When the raw material is charged by using one scraper 3 (two scrapersfor the feed from both ends of the belt), the feed amount of the pelletcan be adjusted by shaping the scraper 3 into the curve shape shown inFIGS. 5( a) and 5(b). When this scraper 3 is used, a greater amount ofthe raw material can be fed to the outer periphery of the rotary hearththan to the inner periphery. Consequently, deviation of the feed amountresulting from the area difference between the inner and outerperipheries of the rotary hearth can be corrected.

Incidentally, in the embodiments shown in FIGS. 2( a) and 2(b) to FIGS.5( a) and 5(b), the raw material 2 may be charged as a single layer intothe flat belt conveyor 1 but when the raw material 2 is charged in twoto five layers, the raw material 2 can be uniformly dispersed.

When the raw material 2 is charged in the single layer onto the flatbelt conveyor 1, the raw material 2 can be uniformly dispersed into thefurnace after it is charged onto the conveyor. When any gaps exist amongthe raw materials, however, the raw materials cannot be disperseduniformly in some cases because only the gaps become smaller andnon-uniformity of the raw materials occurs on the side of the scrapersurface.

Therefore, when the raw materials 2 in two or more layers is chargedonto the conveyor, the layers of raw materials bury the gaps.Consequently, the gaps do not occur among the raw materials but the rawmaterial can be uniformly dispersed and charged into the furnace.

When the number of layers exceeds five layers, on the other hand, thewidth capable of uniformly dispersing the raw material does not changeeven when the raw material 2 is charged onto the conveyor. It istherefore preferred to charge the raw materials in the range of two tofive layers.

INDUSTRIAL APPLICABILITY

The invention can provide a raw material-feeding apparatus capable ofuniformly dispersing and feeding into a furnace raw materials that islikely to undergo dusting, deformation and mutual adhesion. Because{circle around (1)} the invention minimizes the impact to theagglomerated raw material, {circle around (2)} can feed the agglomeratedraw material on the continuous line and {circle around (3)} can feed theagglomerated raw material into the rotary hearth furnace withoutinterruption, the invention provides the following industriallyremarkable effects.

-   1) The agglomerated raw material dust is not fed into the furnace,    and the loss of the furnace refractory and wear of the discharging    device can be drastically reduced.-   2) Cleaning of the agglomerated raw material charging device, in    which closure has frequently occurred, due to deformation and mutual    adhesion becomes unnecessary, and the operation ratio can be    improved.-   3) Because the limitations on agglomeration can be drastically    mitigated, the range of selection of agglomeration methods can be    expanded and a agglomeration methods having a low cost and high    efficiency can be selected.

1. A raw material-feeding apparatus for a rotary hearth furnace, forfeeding raw materials to a rotary hearth furnace by using a flat beltconveyor, characterized in that a scraper for guiding the raw materialson said flat belt conveyor to a side edge of said flat belt conveyor isarranged obliquely to a traveling direction of said flat belt conveyor,wherein the raw materials on said flat bed conveyor are fed to therotary hearth furnace from the side edge of said flat belt conveyor, andwherein a cutoff plate is arranged downward from the carrier surface ofthe flat belt conveyor and adjustment projections are disposed on thesurface of the scraper on which the raw materials flow.
 2. A rawmaterial-feeding apparatus for a rotary hearth furnace according toclaim 1, wherein said scrapers for guiding the raw materials on saidflat belt conveyor to the side edge of said flat belt conveyor aredisposed on both sides of said flat belt conveyor and entrance positionsof the scrapers where the raw material on the flat belt conveyor areguided to the side edge of the flat belt conveyor for falling on therotary hearth furnace are arranged alternatively left and right.
 3. Araw material-feeding apparatus f or a rotary hearth furnace according toclaim 1, wherein a gap between entrance portions of said scraper forguiding the raw materials on said flat belt conveyor to the side edge ofsaid flat belt conveyor is adjustable.
 4. A raw material-feedingapparatus for a rotary hearth furnace according to claim 1, wherein saidscraper for guiding the raw materials on said flat belt conveyor to theside edge of said flat belt conveyor is shaped into a curve shape.
 5. Araw material-feeding apparatus for a rotary hearth furnace according toclaim 1, wherein the raw materials are charged in one layer onto saidflat belt conveyor.
 6. A raw material-feeding apparatus for a rotaryhearth furnace according to claim 1, wherein the raw materials arecharged in two to five layers onto said flat belt conveyor.